­Millions of people trade billions of shares of stock every day on a vast collection of computer systems that are incredibly reliable and, very nearly, error-free. There are so many things happening at once that system becomes difficult to comprehend, and the fact that the it works so well is truly a feat.

So why don't we zoom out and take a high-level picture of the process so that it's possible to see the whole thing? After all, few things are as complex when you look at them from 20,000 feet. Moreover, by understanding our electronic trading system you can fully appreciate one of the most important parts of the American system of capitalism.

Times have changed and so has the price of groceries. Gas was roughly 27 cents a gallon in 1957, so how much less did items cost at the grocery store? Check out this list of grocery store prices for 14 items in 1957, including ground beef, butter, and mil